Realization of very long wavelength infrared photovoltaic detector arrays on mercury cadmium telluride epitaxial layers grown on Si substrates

This paper proposes a development of n-on-p structures for realizing very long wavelength infrared (VLWIR) detector arrays on mercury cadmium telluride (HgCdTe) epitaxial layers grown on Si substrates. It is shown from a comparative study of zero-bias resistance-area product (R₀A) of diodes in n-on-p and p-on-n configurations that the n-on-p structure has promising potential to control contribution of dislocations, without actually reducing dislocation density below the current level (mid-10⁶ cm⁻²) of HgCdTe/Si material technology. The resulting gain will be in terms of both higher numerical magnitudes of R₀A and its reduced scatter.     

Direct Pyrolysis of Raw Rice Husks for Maximization of Silicon Carbide Whisker Formation

A new alternate route for the production of SiC from rice husks has been described. The proposed single-stage process has the advantage of reduced time of production and a much higher yield of SiC whiskers than the conventional two-stage process. Direct pyrolysis of raw rice husks was carried out in a graphite furnace under vacuum and the reaction products were analyzed through macroscopic examination, XRD, SEM, and chemical analysis. Effects of time and temperature on the relative yields of the various reaction products have been determined over a wide range. The pyrolysis of raw rice husks has been found to be accompanied by four different competitive processes, viz., formation of SiC whiskers, formation of SiC polycrystals, crystallization of amorphous silica, and graphitization of amorphous carbon. Crystallization of silica and formation of SiC( w ) are dominant processes at 1150° to 1310°C. At higher temperatures formation of SiC polycrystals and graphitization of carbon are more favored. A multistep pyrolysis to 1310°C was found to yield a still higher amount of SiC( w ) than direct pyrolysis.     

Primary lymphoreticular tumors of the orbit

Primary orbital lymphomas are rare. We report nine such cases (4 with DWDL, 3 with DPDL, 1 with DHL and 1 unclassifiable lymphoma). All patients achieved clinical complete remission (CR). Of those who completed treatment more than a year ago, three continue to be in CR at 17, 24 & 25 months and two are lost to follow up.     

Analysis of playout strategies for voice transmission using packet switching techniques

Due to variations in network delay, a stream of voice packets with deterministic interarrival times to a data network may not have deterministic interdeparture times at the destination. Two playout schemes which are designed to remove such variations in delay are considered. Analytic results for the performance of these two schemes are obtained. Numerical examples showing the effect of coefficient of variation of interdeparture time on performance are presented.     

Comparative evaluation of fine needle aspiration cytology and biopsy of testis in diagnosis of male infertility

Infertility has a fair degree of male factor contribution in its aetiology, hence needs complete evaluation of male partner especially the status of spermatogenesis. In the present study comparative evaluation of fine needle aspiration cytology (FNAC) and biopsy of testis showed 90% accuracy of FNAC in respect of histopathological diagnosis of spermatogenesis. FNAC is a safe, fairly accurate, outdoor investigation in infertile man and it is devoid of the complications of haematoma formation, suppression of spermatogenesis and antigenic stimulation as seen with testicular biopsy.     

Molecular architecture of the lactococcal cell surface as it relates to important industrial properties

From an industrial perspective there are a number of important properties of lactococci that are either carried on, or are controlled and regulated by, the cell surface e.g. phage adsorption, exopolysaccharide production, cell aggregation/sedimentation, cell autolysis and the translocation of foreign DNA. Lactococcus lactis subsp. cremoris strain E8 and its spontaneous phage-resistant variant strain 398 were used as a model system to study the molecular architecture of the lactococcal cell surface and to identify the cell wall components that are involved in phage adsorption. Genetically, the two strains were found to be very closely related as determined by the comparison of chromosomal DNA and plasmid profiles.

Two major cell wall components of both strains were the accessory polysaccharides and peptidoglycan, the latter containing, Asp, Glu, Lys and Ala in molar ratio of 1:1:1:2, respectively. There were, however, significant quantitative differences in the levels of monosaccharide in accessory polysaccharide of the two strains; the parent strain contained 15-fold more galactose and 3-fold more glucosamine.

In order to identify the components of the cell wall involved in phage adsorption, the cell walls from the parent strain (strain E8) were subjected to various chemical and enzymatical treatments before testing their ability to adsorb different phages. The result indicated that the essential component of the phage receptor in the cell wall of Lc. lactis subsp. cremoris strain E8 was carbohydrate in nature and was covalently linked to the peptidoglycans. Lectin binding experiments revealed that galactose and glucosamine were required for the adsorption of phages. An electron microscopic study of the interaction between the phages and their host showed that phages adsorb to a limited number of receptor sites which were distributed over the entire cell envelope.     

The rates of solar energy storage and retrieval in a zeolite-water system

The salient features that determine the possible use of a water vapour-zeolite 13X system as a method of energy storage were investigated. Cycling studies over two months revealed no decrease in water capacity nor any structural deterioration. The rate at which water could be desorbed in a static situation was determined at various temperatures from 110 to 250°C. The adsorption isotherm and the heats of adsorption as a function of amount of adsorbed water were determined. The saturation capacity was 0.33 g H₂O/g zeolite while the heat of adsorption declined from 90 to 50 kJ mol⁻¹. The rate of heat development was found to be very high so that heat extraction from the store would not be a problem in any practical utilization of this system.     

The communication system

The paper discusses the salient features of system design considerations for both uplink and downlink, subsystem details and the in-orbit performance of the communication system forAryabhata.     

Reliability Education in India?Present and Future

This paper surveys the present status and efforts in formal and informal reliability education in India. Survey of important research activities as indicated by the published research papers in this Transactions for the last five years is also included. A three phase programme for future training in reliability for developing countries like India is suggested. Phase one consists of immediate introduction of an elective course for all disciplines of engineering at undergraduate level which should be gradually converted into a compulsory course. Phase two consists of introducing a specialized 2-year postgraduate programe in reliability engineering. Brief course details for both these phases are given. Phase three is the establishment of a National Reliability Research Centre to coordinate, direct, and advance research activities.